Switch control circuit, switch control method and converter using the same

ABSTRACT

Provided is a switch control circuit for controlling a current control switch of a power supply, the power supply including a load, an inductor and the current control switch that are series-coupled to an input power. The switch control circuit includes a current measuring unit configured to measure a current flowing into the load, a current integral unit configured to integrate the measured current, a comparison unit configured to compare the integrated current value and a reference value and a control unit coupled to the current control switch, the control unit being configured to turn off the current control switch when the integrated current is substantially the same as the reference value and turn on the current control switch when a predefined off-time elapses from a time when the current control switch is turned off. The switch control circuit may quickly and accurately control an average current.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 USC §119(a) of KoreanPatent Application No. 10-2014-0027968 filed on Mar. 10, 2014, in theKorean Intellectual Property Office, the entire disclosure of which isincorporated herein by reference for all purposes.

BACKGROUND

1. Field

The following description relates to a switch control technology. Thefollowing description also relates to a switch control circuit, method,and a converter using the same capable of controlling a stable averagecurrent regardless of an input change, a peripheral parts change, a loadchange or a switch off-time.

2. Description of Related Art

A power supply is an apparatus that supplies a power to a load. A buckconverter, one of the power supplies, corresponds to a step-down DC-DCconverter. That is, such a converter outputs a voltage that is lowerthan an input voltage. The buck converter uses an inductor and twoswitches, for example, where the two switches are a transistor and adiode, controlling the inductor to repeatedly perform a process ofstoring an energy supply in the inductor and that of discharging theinductor to a load.

A linear regulator may be used instead of a buck converter to lower thevoltage of a DC power supply. However, the use of a linear regulatorpresents an issue that the waste of energy that occurs as it operates ishigh because a linear regulator operates in a manner that involves asignificant portion of the extra power being exhausted into a heat.Meanwhile, when a buck converter is implemented as an integratedcircuit, the buck converter is commonly used because at least 95% of thepower supplied to it can be converted.

The buck converter coupled with a LED (Light Emitting Diode) may includea switch controlling a current that flows to the LED, a sensing circuitthat measures the load current, for example for a load series-coupled tothe LED and the inductor, and a control circuit controlling the switchbased on the measured load current to control constantly maintaining aload average current.

Various technologies relate to an average inductor current modeswitching converters and relate to a control circuit and a method forregulating an average inductor current in switching converter. Thesetechnologies disclose aspects of a control circuit controlling a loadcurrent on the power supply.

FIG. 1 illustrates a waveform diagram of a load current controlled by acontrol circuit.

Referring to FIG. 1, an x-axis and a y-axis respectively represent atime and a current value. Thus, FIG. 1 illustrates how the load currentchanges over time.

The control circuit of FIG. 1 senses a current that flows to a loadthrough a sensing circuit and stores a time when a sensed currentreaches a predefined reference current value REF. For example, thecontrol circuit stores a reach time T1, where the reach time T1indicates a time from when a switch controlling a current is turned onto a time when the sensed current reaches the predefined referencecurrent value REF.

The control circuit counts the reach time T1 stored at a time when thesensed current reaches the predefined reference current REF and turnsoff a switch at an elapsed time T2 corresponding to the reach time T1.The average current of the load current is maintained at the predefinedreference current REF.

In such a control circuit, the load current is assumed to constantlyincrease. However, when the load current does not constantly change,there is an issue that it is difficult to control the average current sothat the average current is substantially the same as the referencecurrent.

Also, such a control circuit includes an intermediate operationalcircuit for determining the reach time when the sensed current reachesthe reference current and storing the determined reach time. Therefore,such a control circuit presents issues that a delay time for a currentcontrol occurs and it is difficult to control the average currentaccording to a change of the input power and the load.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

Examples provide a switch control technology of a power supply devicecapable of quickly and accurately performing an average current control.

Examples provide a switch control technology of a power supply devicecapable of performing a current control in real-time.

In one general aspect, a switch control circuit for controlling acurrent control switch of a power supply, the power supply including aload, an inductor and the current control switch that are series-coupledto an input power includes a current measuring unit configured tomeasure a current flowing into the load, a current integral unitconfigured to integrate the measured current, a comparison unitconfigured to compare the integrated current value and a referencevalue, and a control unit that is coupled to the current control switch,the control unit being configured to turn off the current control switchin response to the integrated current value being substantially same asthe reference value and to turn on the current control switch inresponse to a predefined off-time having elapsed from a time when thecurrent control switch is turned off.

The current control switch may be a Metal-Oxide-Semiconductor FieldEffect Transistor (MOSFET).

The current measuring unit may include a current measuring resistorcoupled between one terminal of the current control switch and thereference voltage and configured to measure a voltage at both sides ofthe current measuring resistor.

The current integral unit may include a V-I converter configured toconvert the measured voltage to a current.

The current integral unit may integrate a predefined reference currentto generate the reference value, varying according to time.

The current integral unit may include a first dependent current sourceconfigured to supply a first current having a value that issubstantially the same as the measured current value, a second dependentcurrent source configured to supply a second current having a value thatis substantially the same as a reference current value related to thereference value, and a pair of capacitors that are respectivelyseries-coupled to the first and second dependent current sources,wherein the current integral unit performs integration operations on themeasured current and the reference current through each of the pair ofcapacitors.

The second dependent current source may include a differential amplifiercircuit, wherein the differential amplifier circuit doubly amplifies thereference current to amplify a difference between the amplifiedreference current and the measured current.

The current integral unit may include a constant current sourceconfigured to supply a specific current, a first switch that isseries-coupled to the constant current source, the first switch beingconfigured to be controlled by the measured current, a second switchthat is series-coupled to the constant current source, the second switchbeing configured to be controlled by a reference current related to thereference voltage, and a pair of capacitors that are respectivelyseries-coupled to the first and second switches, the pair of capacitorsbeing configured to perform integration operations on currents flowinginto the first and second switches.

The comparison unit may be a differential amplifier.

The control unit may include an off-time control unit configured tocount the predefined off-time from a time at which the current controlswitch is turned off, and a switch driving unit configured to controlthe current control switch based on outputs of the comparison unit andthe off-time control unit.

The switch driving unit may be an SR latch configured to perform NOR orNAND logic operations on outputs of the comparison unit and the off-timecontrol unit.

In another general aspect, a switch control method performed in a switchcontrol circuit for controlling a current control switch of a powersupply, the power supply including a load, an inductor and the currentcontrol switch that are series-coupled to an input power includesmeasuring a current flowing into the load, integrating the measuredcurrent, comparing the integrated current value and a reference value,turning off the current control switch in response to the integratedcurrent value being substantially same as the reference value, andturning on the current control switch in response to a predefinedoff-time elapsing from a time when the current control switch is turnedoff.

In another general aspect, a converter includes a load that isseries-coupled to an input power, an inductor that is series-coupled tothe load, a current control switch that is series-coupled to theinductor, the current control switch being configured to control acurrent flowing into the load, a freewheeling diode that isparallel-coupled to the load and the inductor that are series-coupledwith each other, and a switch control circuit configured to control thecurrent control switch, wherein the switch control circuit includes acurrent measuring unit configured to measure a current flowing into theload, a current integral unit configured to integrate the measuredcurrent, a comparison unit configured to compare the integrated currentvalue and a reference value, and a control unit that is coupled to thecurrent control switch, the control unit being configured to turn offthe current control switch in response to the integrated current valuebeing substantially the same as the reference value and to turn on thecurrent control switch in response to a predefined off-time elapsingfrom a time when the current control switch is turned off.

In another general aspect, a switch control circuit for controlling acurrent control switch includes a current measuring unit configured tomeasure a current flowing into a load that is series-coupled to an inputpower, wherein the load, an inductor, and the current control switch areseries-coupled to an input power, a current integral unit configured tointegrate the measured current, a comparison unit configured to comparethe integrated current value and a reference value, and a control unitthat is coupled to the current control switch, the control unit beingconfigured to turn off the current control switch in response to theintegrated current value being substantially same as the reference valueand to turn on the current control switch in response to a predefinedoff-time have elapsed from a time when the current control switch isturned off.

The current control switch may be a Metal-Oxide-Semiconductor FieldEffect Transistor (MOSFET).

The current measuring unit may include a current measuring resistorcoupled between one terminal of the current control switch and thereference voltage and configured to measure a voltage at both sides ofthe current measuring resistor.

The current integral unit may include a first dependent current sourceconfigured to supply a first current having a value that issubstantially the same as the measured current value, a second dependentcurrent source configured to supply a second current having a value thatis substantially the same as a reference current value related to thereference value, and a pair of capacitors that are respectivelyseries-coupled to the first and second dependent current sources,wherein the current integral unit performs integration operations on themeasured current and the reference current through each of the pair ofcapacitors.

The second dependent current source may include a differential amplifiercircuit, wherein the differential amplifier circuit doubly amplifies thereference current to amplify a difference between the amplifiedreference current and the measured current.

The current integral unit may include a constant current sourceconfigured to supply a specific current, a first switch that isseries-coupled to the constant current source, the first switch beingconfigured to be controlled by the measured current, a second switchthat is series-coupled to the constant current source, the second switchbeing configured to be controlled by a reference current related to thereference voltage, and a pair of capacitors that are respectivelyseries-coupled to the first and second switches, the pair of capacitorsbeing configured to perform integration operations on currents flowinginto the first and second switches.

The control unit may include an off-time control unit configured tocount the predefined off-time from a time at which the current controlswitch is turned off, and a switch driving unit configured to controlthe current control switch based on outputs of the comparison unit andthe off-time control unit.

The described examples have the following advantages. However, this doesnot mean that all examples include all the following advantages or arelimited to include just the following advantages.

The switch control technology according to examples respectivelyintegrates and compares the measured current and the reference current.By so doing, examples quickly and accurately perform an average currentcontrol.

Thus, the switch control technology according to examples performs acurrent control in real time through current integration operations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a waveform diagram of a load current controlled by acontrol circuit.

FIG. 2 is a circuit diagram illustrating a converter according to anexample.

FIGS. 3A-3C are a circuit diagram and a wave diagram illustrating thecurrent integral unit of FIG. 2 according to an example.

FIGS. 4A-4C are a circuit diagram and a wave diagram illustrating thecurrent integral unit of FIG. 2 according to another example.

FIGS. 5A-5C are a circuit diagram and wave diagram illustrating thecurrent integral unit of FIG. 2 according to the other example.

Throughout the drawings and the detailed description, unless otherwisedescribed or provided, the same drawing reference numerals will beunderstood to refer to the same elements, features, and structures. Thedrawings may not be to scale, and the relative size, proportions, anddepiction of elements in the drawings may be exaggerated for clarity,illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the systems, apparatuses and/ormethods described herein will be apparent to one of ordinary skill inthe art. The progression of processing steps and/or operations describedis an example; however, the sequence of and/or operations is not limitedto that set forth herein and may be changed as is known in the art, withthe exception of steps and/or operations necessarily occurring in acertain order. Also, descriptions of functions and constructions thatare well known to one of ordinary skill in the art may be omitted forincreased clarity and conciseness.

The features described herein may be embodied in different forms, andare not to be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided so thatthis disclosure will be thorough and complete, and will convey the fullscope of the disclosure to one of ordinary skill in the art.

Terms used in the present disclosure may be understood as follows.

While terms such as “first” and “second,” etc., may be used to describevarious components, such components are not to be understood as beinglimited to the above terms. The above terms are used only to distinguishone component from another. For example, a first component may bereferred to as a second component without departing from the scope ofthe present disclosure, and likewise a second component may be referredto as a first component.

It is to be understood that when an element is referred to as being“coupled to” another element, such an element in some examples isdirectly coupled to the other element or intervening elements may alsobe present. In contrast, when an element is specifically referred to asbeing “directly coupled to” another element, no intervening elements arepresent. Also, unless explicitly specified to the contrary, the word“comprise” and variations such as “comprises” or “comprising,” are to beunderstood to imply the inclusion of stated elements but do not implythe exclusion of any other elements. Meanwhile, other expressionsdescribing relationships between components such as “˜between”,“immediately˜between” or “adjacent to˜” and “directly adjacent to˜” areto be interpreted similarly.

Singular forms “a”, “an” and “the” in the present disclosure areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It is to be further understood that terms such as“including” or “having,” etc., are intended to indicate the existence ofthe features, numbers, operations, actions, components, parts, orcombinations of such disclosed in the specification in certain examples,and are not intended to preclude the possibility that one or more otherfeatures, numbers, operations, actions, components, parts, orcombinations thereof exist or are added in other examples.

The terms used in the present application are merely used to describevarious examples, and are not intended to limit the present disclosure.Unless otherwise defined, all terms used herein, including technical orscientific terms, have the same meanings as those generally understoodby those with ordinary knowledge in the field of art to which thepresent disclosure belongs in view of the present disclosure. Such termsas those defined in a generally used dictionary are to be interpreted tohave the meanings equal to the contextual meanings in the relevant fieldof art, and are not to be interpreted to have ideal or excessivelyformal meanings unless clearly so defined in the present disclosure.

FIG. 2 is a circuit diagram illustrating a converter according to anexample.

Referring to FIG. 2, a converter 200 includes a load 210, an inductor220, a freewheeling diode 230, a current control switch 240 and a switchcontrol circuit 260.

The converter 200 corresponds to a power supply. For example, theconverter 200 is a buck converter outputting a voltage being lower thanan input voltage.

The load 210 corresponds to an element that is series-coupled to aninput voltage VIN. For example, the load 210 element consumes an energy.In an example, the load 210 is implemented as a LED (Light EmittingDiode) device.

The inductor 220 stores energy supplied by an input power or releasesthe stored energy according to an operation of the current controlswitch 240. The operation of the current control switch 240 is to bedescribed further below. In this example, the inductor 220 induces avoltage that is proportional to a change amount of a current input tothe inductor 220 to suppress a sudden change of the current and store anenergy of a quantity that is proportional to a square of the currentinput to the inductor 220.

For example, turn-on and turn-off periods of the current control switch240 are changed in response to one another according to a variableinductor capacity. Therefore, an operational frequency of the currentcontrol switch 240 is changed in response to turn-on and turn-offperiods.

In the example of FIG. 2, the freewheeling diode 230 forms a currentmovement loop providing a corresponding energy to the load 210 when theenergy is output by the inductor 220. Furthermore, the freewheelingdiode 230 outputs the stored energy in the inductor 220 to the load 210to consume the stored energy in the inductor 220 when the currentcontrol switch 240 is turned off. Also, in the example of FIG. 2, thefreewheeling diode 230 prevents damage to the converter 200, such asdamage to the current control switch 240 caused by a spark, caused bythe flow of the charged current from the inductor 220 into the currentcontrol switch 240.

In the example of FIG. 2, the current control switch 240 isseries-coupled to the inductor 220 and repeatedly performs turn-on andturn-off operations to control a current amount flowing into the load210.

Also in examples, the current control switch 240 is turned on or turnedoff by a control signal and selectively provides the movement loop ofthe current flowing into the inductor 220 according to the turned-on orturned-off state of the current control switch 240.

When current control switch 240 is turned on, the current flows into theinductor 220 supplied by the input power, the energy accumulates in theinductor 220 and the current increasingly flows into the load 210.

Afterward, when current control switch 240 is turned off, the currentmovement loop is formed so that an inductor current, that is, a currentderived from the energy accumulated in the inductor 220, flows into theload 210 through the freewheeling diode 230. The inductor currentdecreases until the current control switch 240 is turned on. Meanwhile,in the example of FIG. 2, the converter 200 repeatedly turns on andturns off the current control switch 240 to output a pulse-type current.

The switch control circuit 260 controls an operation of the currentcontrol switch 240. More specifically, in examples, the switch controlcircuit 260 measures the current flowing into the load 210 to controlthe operation of the current control switch 240 based on a referencevoltage and a result of an integration operation that integrates themeasured current. Hereinafter, a switch control circuit 260 is describedfurther.

Referring to FIG. 2, the switch control circuit 260 includes a currentmeasuring unit, a current integral unit 261, a comparison unit 262 and acontrol unit.

In the example of FIG. 2, the current measuring unit measures thecurrent flowing into the load 210. In the example of FIG. 2, the currentmeasuring unit includes a current measuring resistor 250 coupled betweenone terminal of the current control switch 240 and a reference voltageof the circuit to measure the current flowing into the load 210 based ona voltage at both sides of the current measuring resistor 250, orsimilarly, a voltage at CS terminals.

In one example, the current measuring unit includes a voltage-to-current(V-I) converter converting the voltage at both sides of the currentmeasuring resistor 250 to the measured current. In this example, the V-Iconverter is installed at a terminal for measuring a current in theswitch control circuit 260. Meanwhile, the V-I converter is arrangedbetween the current measuring unit and current integral unit 261. In anexample, the V-I converter is included in the current integral unit 261.

In this example, the current integral unit 261 performs an integrationoperation on the measured current.

In one example, the current integral unit 261 integrates a predefinedreference current to generate an appropriate reference voltage thatvaries according to time. In one example, the predefined referencecurrent is set in the manufacturing process or in another example isvaried by a pin providing the current installed in an outside of thecurrent integral unit 261 or a specific program that sets such acurrent. In another example, the predefined reference current is set bya user through an Average terminal, where the Average terminal is acomputer with input capability that allows the user to set thepredefined reference current.

For example, the current integral unit 261 receives the current measuredin the current measuring unit and the predefined reference current. Thecurrent integral unit 261 then performs the integration operation oneach of them.

A configuration of the current integral unit 261 is described withreference to FIGS. 3 through 5.

In one example, the current integral unit 261 performs the integrationoperation while the current control switch 240 is turned on. In thisexample, the current integral unit 261 is reset at a time when thecurrent control switch 240 is turned off. For example, the currentintegral unit 261 provides an energy accumulated in a capacitor and isto be reset at a time when the current control switch 240 is turned off.

In this example, the comparison unit 262 compares the current valueintegrated in the current integral unit 261 and the reference voltage.As part of this comparison, the reference voltage corresponds to anincreasing form according to a specific slope or corresponds to anintegration result of integrating the predefined reference current inthe current integral unit 261. As discussed below, the reference voltageis assumed to the integrated reference current.

In this example, the comparison unit 262 compares each of the currentvalues integrated in the current integral unit 261, as discussedpreviously.

Further, the comparison unit 262 compares an integral value of themeasured current, that is, a first integral value and an integral valueof the reference current or the reference voltage, that is, a secondintegral value.

In one example, the comparison unit 262 is implemented as an amplifier,such as a differential amplifier.

For example, the comparison unit 262 compares the first and secondintegral values by output the difference of the integral values, forexample by calculating the first integral value minus the secondintegral value. Because the reference value is greater than that of themeasured current at a time when the current control switch 240 is turnedon, the comparison unit 262 may output a negative value, indicated by alow level or 0. As time passes, because the current value flowed to theload 210 increases, the comparison unit 262 may output a positive value,indicated by a high level or 1.

The control unit is coupled to the current control switch 240 and turnsoff the current control switch 240 when the integrated current value issubstantially same with that of the reference value as determined usingthe comparison unit 262. In this example, the control unit is coupled toa gate terminal of the current control switch 240.

Further, in this example, the control unit generates a control signalthat turns on the current control switch 240 to control the currentcontrol switch 240 so that the current control switch forms a currentmovement loop that flows a current into the load 210 by the input power.

Afterwards, the control unit generates a control signal turning off thecurrent control switch 240 to cut off the current flowing into thecurrent movement loop from the input power when an output sign of thecomparison unit 262 changes, such as from a negative value to a positivevalue. That is, such a sign change occurs when the integrated measuringcurrent is substantially same as that of the reference voltage, oralternatively when each of the integrated current values issubstantially same as one another.

Also, the control unit generates a control signal turning on the currentcontrol switch 240 to form the current movement loop that outputs thecurrent into the load 210 through the current control switch 240 by theinput power when a specific time elapses after a turn-off time of thecurrent control switch 240. In an example, such a specific time is apredefined off-time.

In one example, the control unit includes an off-time control unit 263that counts the predefined off-time from a time at which the currentcontrol switch 240 is turned off. Herein, the turn-off time correspondsto a time from a time at which the current control switch 240 is turnedoff to include the time when the current control switch 240 ismaintained as being turned off.

For example, the off-time control unit 263 outputs a low level signal,for example, a value of 0, during the turn-off time or outputs a highlevel signal, for example, a value of 1, when the turn-off time elapses.

In one example, the off-time control unit 263 further includes a timeset module setting the off-time according to an external input or aspecific program. For example, such off-time is potentially set by auser through an RT-OFF terminal.

In one example, the control unit includes a switch driving unit 264 thatcontrols the current control switch 240 based on outputs of thecomparison unit 262 and the off-time control unit 263.

Further, in an example, the switch driving unit 264 performs a NOR or aNAND logic operation on outputs of the comparison unit 262 and theoff-time control unit 263. The result of such a logic operation is thenoutput as the control signal controlling the current control switch 240.

In one example, the switch driving unit 264 is implemented as an SRlatch that performs a NOR or NAND logic operation on the outputs of thecomparison unit 262 and the off-time control unit 263.

In such an example, the input terminals S and R of the SR latchrespectively receive the outputs of the off-time control unit 263 andthe comparison unit 262. In this example, when the input terminal Sreceives the high level signal, such as a value of 1, the SR latchassumes a state of SET to output a control signal that turns on thecurrent control switch 240 from an output terminal Q. Afterward, whenthe input terminal R receives the high level signal, such as a value of1 or a positive signal, according to the output of the comparison unit262, the SR latch assumes a state of RESET to output the control signalthat turns off the current control switch 240 in the output terminal Q.Meanwhile, when the output of the comparison unit 262 reaches the highlevel, the off-time control unit 263 outputs the low level signal.

As a result, the switch control circuit 260 of such an example quicklyand accurately controls the load current to perform the integrationoperation while the current control switch 240 is turned on. Also, theswitch control circuit 260 reflects changes of the input power and theoutput power in real time to accurately control the average current ofthe load in comparison with alternative technologies.

A detailed configuration of the current integral unit 261 in FIG. 2 isdescribed further with references to FIGS. 3 through 5.

FIGS. 3A-3C are a circuit diagram and a wave diagram illustrating thecurrent integral unit of FIG. 2 according to an example.

Referring to FIG. 3A, the current integral unit 261 includes a pair ofdependent current sources and a pair of capacitors respectivelyseries-coupled to the pair of the dependent current sources.

Further, a first dependent current source corresponds to a currentsource that provides a first current I1 in response to the measuredcurrent and a second dependent current source corresponds to a currentsource that provides a second current I2 in response to the referencecurrent.

In this example, the first dependent current source provides the firstcurrent I1, where I1 corresponds to “gm*VCS1”. Herein, “gm” correspondsto a current ratio of the measured current and corresponds to anarbitrary constant. Also, in this example, the second dependent currentsource provides I2, where I2 corresponds to “gm*Average”. In thisexample, the “gm” value of the I2 is substantially same with that of theI1.

The pair of the capacitors in this example performs the integraloperations on each of the measured current and the reference current.

A first node is coupled to an input terminal, for example the +terminal, of the comparison unit 262, and the first node is also coupledto the first dependent current source and the capacitor. A voltage ofthe first node is provided to the input terminal of the comparison unit262, for example the + terminal. Also, a second node is coupled toanother input terminal, for example the − terminal, of the comparisonunit 262, and the second node is also coupled to the second dependentcurrent source and the capacitor. A voltage of the second node isprovided to the input terminal of the comparison unit 262, for examplethe − terminal.

Referring to FIG. 3B, an x-axis and a y-axis respectively represent atime and a current value.

The reference current Average is assumed to be a fixed value that has apredefined value regardless of how much time elapses and the measuredcurrent VCS1 is assumed to constantly increase as time elapses.

Referring to FIG. 3C, an x-axis and a y-axis respectively represent atime and the integrated current value, that is, an integral value, Q.

The current integral unit 261 performs integration operations on each ofthe currents from a time when the current control switch 240 is turnedon, such as indicated by the low level signal or the value of 0. Asillustrated, the integral value of the measured current, that is, thefirst integral value, has a parabolic form because the measured currentconstantly increases in a linear fashion as time elapses and theintegral of a linear function is a quadratic function. Also, theintegral value of the reference current, that is, the second integralvalue, represents a specific sloped form because the reference currenthas a fixed value, and the integral of a constant function is a linearfunction.

As shown in the example, a graph of the first integral value intersectswith that of the second integral value at a time t1 when the firstintegral value is substantially same with the second integral value.That is, t1 may correspond to a time when a graph area under the Averagefunction is substantially same with that of the VCS1 in FIG. 3B.

Meanwhile, in this example, at the time t1, the switch control circuit260 turns off the current control switch 240 and the current integralunit 261 is reset.

In an example, the second dependent source doubly amplifies thereference current and further includes a differential amplifier circuitfor amplifying a difference between the amplified reference current andthe measured current.

FIGS. 4A-4C are a circuit diagram and a wave diagram illustrating thecurrent integral unit in FIG. 2 according to another example.

Referring to FIG. 4A, FIG. 4A represents a similar configuration withFIG. 3A but the size of the current I2 value provided from the seconddependent current source corresponds to “gm*(2*Average−VCS1)”.

Further in FIG. 4A, an internal circuit of the second dependent currentsource includes an amplifier and the second dependent current sourcedoubly amplifies the reference current. The second dependent currentsource amplifies the difference between the amplified reference currentand the measured current to supply I2, where I2 corresponds to“gm*(2*Average−VCS1)”.

Therefore and although an offset occurs in the measured current, theswitch control unit 260 mutually supplements an offset value occurringin the first and second dependent current sources to accurately controlthe current regardless of the offset.

Referring to FIG. 4B, the current of the second dependent current sourceconstantly decreases as time elapses.

Referring to FIG. 4C, the first integral value has a parabolic formbecause the measured current constantly increases in a linear fashion astime elapses and the integral of a linear function is a quadraticfunction and the second integral value has a parabolic form because thecurrent of the second dependent current source constantly decreases in alinear fashion as time elapses. As illustrated in FIG. 3C, the switchcontrol circuit 260 turns off the current control switch 240 and thecurrent integral unit 261 is reset at a time t2 when a graph of thefirst integral value intersects with that of the second integral value.

In one example, the current integral unit 261 includes a constantcurrent source, first and second switches and a pair of capacitors. Theconstant current source supplies a specific current. The first switch isseries-coupled to the constant current source and is controlled by themeasured current. The second switch is series-coupled to the constantcurrent source and is controlled by the reference current. The pair ofcapacitors is respectively series-coupled to the first and secondswitches and performs an integration operation on a current that flowsthrough the first and second switches.

FIGS. 5A-5C are a circuit diagram and wave diagram illustrating thecurrent integral unit in FIG. 2 according to another example.

Referring to FIG. 5A, the current integral unit 261 includes a constantcurrent source and first and second switches that are respectivelyseries-coupled to the constant current source.

As one constant current source is illustrated, this means current valuesI3 respectively flowing into the first and second switches aresubstantially the same. Also, the constant current source is implementedin another example as two constant current sources and in such anexample current values supplied from the two constant current sourcesare also substantially the same.

In such an example, a current value flowing from the first switch intothe first capacitor is decided based on that of the measured current anda current value flowing from the second switch into the second capacitoris decided based on that of the reference current.

Referring FIG. 5B, the reference current Average is assumed to a fixedvalue having a predefined value regardless of time elapsed and themeasured current VCS1 is assumed to constantly increase according totime elapsed.

Referring to the example of FIG. 5C, the first integral value, that is aquantity of electric charge accumulated in the first capacitor, rapidlyincreases at a specific time, such as at a time when voltage exceeds athreshold voltage of the switch, because a current value passing throughthe first switch constantly increases until the voltage value applied toa gate of the first switch exceeds a constant voltage value applied to agate of the second switch. In such an example, the second integral valueis saturated to a specific value because a current value passing throughthe second switch constantly decreases until the voltage value appliedto a gate of the first switch exceeds a constant voltage value appliedto a gate of the second switch.

As illustrated in FIG. 5C, the switch control circuit 260 turns off thecurrent control switch 240 and the current integral unit 261 is reset ata time t3 when a graph of the first integral value intersects with thatof the second integral value.

For example, the switch control method is performed by the switchcontrol circuit 260, the switch control circuit 260 controls the currentcontrol switch 240 of the power supply, and the power supply includesthe load, the inductor and the current control switch 240 that arerespectively series-coupled to the input power.

The switch control method includes the following operations.

In operation S610, the switch control circuit 260 measures the currentflowing into the load through the current measuring unit.

In operation S620, the switch control circuit 260 integrates themeasured current passing through the current integral unit 261. In thisoperation, the switch control circuit 260 performs integrationoperations on the predefined reference current to generate the referencevoltage.

In operation S630, the switch control circuit 260 compares theintegrated current value and the reference value or integrated referencecurrent in the comparison unit 262.

In operation S640, the switch control circuit 260 turns off the currentcontrol switch 240 using the switch driving unit 264 when the integratedcurrent value is substantially same as that of the reference value.

In an example, the switch control circuit 260 turns on the currentcontrol switch 240 when the predefined off-time elapses from a time whenthe current control switch 240 is turned off.

Accordingly, the switch control circuit 260 counts the off-time from atime when the current control switch 240 is turned off using theoff-time control unit 263 and turns on the current control switch 240using the switch driving unit 264 when the off-time elapses.

The apparatuses and units described herein may be implemented usinghardware components. The hardware components may include, for example,controllers, sensors, processors, generators, drivers, and otherequivalent electronic components. The hardware components may beimplemented using one or more general-purpose or special purposecomputers, such as, for example, a processor, a controller and anarithmetic logic unit, a digital signal processor, a microcomputer, afield programmable array, a programmable logic unit, a microprocessor orany other device capable of responding to and executing instructions ina defined manner. The hardware components may run an operating system(OS) and one or more software applications that run on the OS. Thehardware components also may access, store, manipulate, process, andcreate data in response to execution of the software. For purpose ofsimplicity, the description of a processing device is used as singular;however, one skilled in the art will appreciate that a processing devicemay include multiple processing elements and multiple types ofprocessing elements. For example, a hardware component may includemultiple processors or a processor and a controller. In addition,different processing configurations are possible, such as parallelprocessors.

The methods described above can be written as a computer program, apiece of code, an instruction, or some combination thereof, forindependently or collectively instructing or configuring the processingdevice to operate as desired. Software and data may be embodiedpermanently or temporarily in any type of machine, component, physicalor virtual equipment, computer storage medium or device that is capableof providing instructions or data to or being interpreted by theprocessing device. The software also may be distributed over networkcoupled computer systems so that the software is stored and executed ina distributed fashion. In particular, the software and data may bestored by one or more non-transitory computer readable recordingmediums. The media may also include, alone or in combination with thesoftware program instructions, data files, data structures, and thelike. The non-transitory computer readable recording medium may includeany data storage device that can store data that can be thereafter readby a computer system or processing device. Examples of thenon-transitory computer readable recording medium include read-onlymemory (ROM), random-access memory (RAM), Compact Disc Read-only Memory(CD-ROMs), magnetic tapes, USBs, floppy disks, hard disks, opticalrecording media (e.g., CD-ROMs, or DVDs), and PC interfaces (e.g., PCI,PCI-express, WiFi, etc.). In addition, functional programs, codes, andcode segments for accomplishing the example disclosed herein can beconstrued by programmers skilled in the art based on the flow diagramsand block diagrams of the figures and their corresponding descriptionsas provided herein.

As a non-exhaustive illustration only, a terminal/device/unit describedherein may refer to mobile devices such as, for example, a cellularphone, a smart phone, a wearable smart device (such as, for example, aring, a watch, a pair of glasses, a bracelet, an ankle bracket, a belt,a necklace, an earring, a headband, a helmet, a device embedded in thecloths or the like), a personal computer (PC), a tablet personalcomputer (tablet), a phablet, a personal digital assistant (PDA), adigital camera, a portable game console, an MP3 player, aportable/personal multimedia player (PMP), a handheld e-book, an ultramobile personal computer (UMPC), a portable lab-top PC, a globalpositioning system (GPS) navigation, and devices such as a highdefinition television (HDTV), an optical disc player, a DVD player, aBlu-ray player, a setup box, or any other device capable of wirelesscommunication or network communication consistent with that disclosedherein. In a non-exhaustive example, the wearable device may beself-mountable on the body of the user, such as, for example, theglasses or the bracelet. In another non-exhaustive example, the wearabledevice may be mounted on the body of the user through an attachingdevice, such as, for example, attaching a smart phone or a tablet to thearm of a user using an armband, or hanging the wearable device aroundthe neck of a user using a lanyard.

While this disclosure includes specific examples, it will be apparent toone of ordinary skill in the art that various changes in form anddetails may be made in these examples without departing from the spiritand scope of the claims and their equivalents. The examples describedherein are to be considered in a descriptive sense only, and not forpurposes of limitation. Descriptions of features or aspects in eachexample are to be considered as being applicable to similar features oraspects in other examples. Suitable results may be achieved if thedescribed techniques are performed in a different order, and/or ifcomponents in a described system, architecture, device, or circuit arecombined in a different manner and/or replaced or supplemented by othercomponents or their equivalents. Therefore, the scope of the disclosureis defined not by the detailed description, but by the claims and theirequivalents, and all variations within the scope of the claims and theirequivalents are to be construed as being included in the disclosure.

What is claimed is:
 1. A switch control circuit for controlling acurrent control switch of a power supply, the power supply comprising aload, an inductor and the current control switch that are series-coupledto an input power, the switch control circuit comprising: a currentmeasuring unit configured to measure a current flowing into the load; acurrent integral unit configured to integrate the measured current; acomparison unit configured to compare the integrated current value and areference value; and a control unit that is coupled to the currentcontrol switch, the control unit being configured to turn off thecurrent control switch in response to the integrated current value beingsubstantially same as the reference value and to turn on the currentcontrol switch in response to a predefined off-time having elapsed froma time when the current control switch is turned off.
 2. The switchcontrol circuit of claim 1, wherein the current control switch is aMetal-Oxide-Semiconductor Field Effect Transistor (MOSFET).
 3. Theswitch control circuit of claim 1, wherein the current measuring unitcomprises a current measuring resistor coupled between one terminal ofthe current control switch and the reference voltage and configured tomeasure a voltage at both sides of the current measuring resistor. 4.The switch control circuit of claim 3, wherein the current integral unitcomprises a V-I converter configured to convert the measured voltage toa current.
 5. The switch control circuit of claim 1, wherein the currentintegral unit integrates a predefined reference current to generate thereference value, varying according to time.
 6. The switch controlcircuit of claim 1, wherein the current integral unit comprises: a firstdependent current source configured to supply a first current having avalue that is substantially the same as the measured current value; asecond dependent current source configured to supply a second currenthaving a value that is substantially the same as a reference currentvalue related to the reference value; and a pair of capacitors that arerespectively series-coupled to the first and second dependent currentsources, wherein the current integral unit performs integrationoperations on the measured current and the reference current througheach of the pair of capacitors.
 7. The switch control circuit of claim6, wherein the second dependent current source comprises a differentialamplifier circuit, wherein the differential amplifier circuit doublyamplifies the reference current to amplify a difference between theamplified reference current and the measured current.
 8. The switchcontrol circuit of claim 1, wherein the current integral unit comprises:a constant current source configured to supply a specific current; afirst switch that is series-coupled to the constant current source, thefirst switch being configured to be controlled by the measured current;a second switch that is series-coupled to the constant current source,the second switch being configured to be controlled by a referencecurrent related to the reference voltage; and a pair of capacitors thatare respectively series-coupled to the first and second switches, thepair of capacitors being configured to perform integration operations oncurrents flowing into the first and second switches.
 9. The switchcontrol circuit of claim 1, wherein the comparison unit is adifferential amplifier.
 10. The switch control circuit of claim 1,wherein the control unit comprises: an off-time control unit configuredto count the predefined off-time from a time at which the currentcontrol switch is turned off; and a switch driving unit configured tocontrol the current control switch based on outputs of the comparisonunit and the off-time control unit.
 11. The switch control circuit ofclaim 10, wherein the switch driving unit is an SR latch configured toperform NOR or NAND logic operations on outputs of the comparison unitand the off-time control unit.
 12. A switch control method performed ina switch control circuit for controlling a current control switch of apower supply, the power supply comprising a load, an inductor and thecurrent control switch that are series-coupled to an input power, theswitch control method comprising: measuring a current flowing into theload; integrating the measured current; comparing the integrated currentvalue and a reference value; turning off the current control switch inresponse to the integrated current value being substantially same as thereference value; and turning on the current control switch in responseto a predefined off-time elapsing from a time when the current controlswitch is turned off.
 13. A converter comprising: a load that isseries-coupled to an input power; an inductor that is series-coupled tothe load; a current control switch that is series-coupled to theinductor, the current control switch being configured to control acurrent flowing into the load; a freewheeling diode that isparallel-coupled to the load and the inductor that are series-coupledwith each other; and a switch control circuit configured to control thecurrent control switch, wherein the switch control circuit comprises acurrent measuring unit configured to measure a current flowing into theload, a current integral unit configured to integrate the measuredcurrent, a comparison unit configured to compare the integrated currentvalue and a reference value, and a control unit that is coupled to thecurrent control switch, the control unit being configured to turn offthe current control switch in response to the integrated current valuebeing substantially the same as the reference value and to turn on thecurrent control switch in response to a predefined off-time elapsingfrom a time when the current control switch is turned off.
 14. A switchcontrol circuit for controlling a current control switch, the switchcontrol circuit comprising: a current measuring unit configured tomeasure a current flowing into a load that is series-coupled to an inputpower, wherein the load, an inductor, and the current control switch areseries-coupled to an input power; a current integral unit configured tointegrate the measured current; a comparison unit configured to comparethe integrated current value and a reference value; and a control unitthat is coupled to the current control switch, the control unit beingconfigured to turn off the current control switch in response to theintegrated current value being substantially same as the reference valueand to turn on the current control switch in response to a predefinedoff-time have elapsed from a time when the current control switch isturned off.
 15. The switch control circuit of claim 14, wherein thecurrent control switch is a Metal-Oxide-Semiconductor Field EffectTransistor (MOSFET).
 16. The switch control circuit of claim 14, whereinthe current measuring unit comprises a current measuring resistorcoupled between one terminal of the current control switch and thereference voltage and configured to measure a voltage at both sides ofthe current measuring resistor.
 17. The switch control circuit of claim14, wherein the current integral unit comprises: a first dependentcurrent source configured to supply a first current having a value thatis substantially the same as the measured current value; a seconddependent current source configured to supply a second current having avalue that is substantially the same as a reference current valuerelated to the reference value; and a pair of capacitors that arerespectively series-coupled to the first and second dependent currentsources, wherein the current integral unit performs integrationoperations on the measured current and the reference current througheach of the pair of capacitors.
 18. The switch control circuit of claim17, wherein the second dependent current source comprises a differentialamplifier circuit, wherein the differential amplifier circuit doublyamplifies the reference current to amplify a difference between theamplified reference current and the measured current.
 19. The switchcontrol circuit of claim 14, wherein the current integral unitcomprises: a constant current source configured to supply a specificcurrent; a first switch that is series-coupled to the constant currentsource, the first switch being configured to be controlled by themeasured current; a second switch that is series-coupled to the constantcurrent source, the second switch being configured to be controlled by areference current related to the reference voltage; and a pair ofcapacitors that are respectively series-coupled to the first and secondswitches, the pair of capacitors being configured to perform integrationoperations on currents flowing into the first and second switches. 20.The switch control circuit of claim 14, wherein the control unitcomprises: an off-time control unit configured to count the predefinedoff-time from a time at which the current control switch is turned off;and a switch driving unit configured to control the current controlswitch based on outputs of the comparison unit and the off-time controlunit.